Populus

Populus is a large group of deciduous (leaf-losing) trees that can attain great heights. These trees, commonly known as Aspen, Poplar and Cottonwood trees, are found in Europe, Asia and North America. Some are found wild in other regions, one being a native of tropical Africa. It is difficult to say how many wild kinds there are, because these trees hybridize very easily. Some of the Poplars are very pretty in bloom, especially the male forms, which may also have reddish leaves when they are young. Male (staminate) and female (pistillate) flowers grow on different trees. The fruits are small, narrowly conical and produced in drooping strands. When they are ripe, they release small seeds, which have a mass of long, silky hairs to aid in their distribution by the wind. This cottony appearance is what gives the name "Cottonwood" to some species. Some Poplar trees are good shade trees and they withstand heavy pruning. Some are great for planting as street trees, but use precaution when planting because they have invasive roots that travel far in search of moisture and may clog drains and sewers and heave up pavements. The branches of these trees are brittle and are susceptible to storm damage. Poplars grow quickly and are known to have reached a 50-foot height in 15 years. Several kinds of Poplars form a small group known as Aspens. Adult trees have rounded leaves with indented edges. Young trees have leaves that vary in size and shape. The leaves of the trees quiver constantly even on the calmest days. Various legends have come about because of this, but it is because the leafstalks are flat, not rounded as other trees. P. tremuloides (Quaking or Trembling Aspen) is a smaller tree, only growing 30 to 40 feet high with a diameter of 8 to 15 inches. Its leaves are roundish or slightly ovate and the edges are very finely and evenly toothed; they grow about 1 or 2 inches long. They are thin, but strong, and shiny, bright green above and pale green beneath. The male form of this tree is very attractive, because its purplish catkins are very noticeable in the spring. It grows into a nice round-topped tree and it spreads by root suckers, which often form thickets. This is one of the leading pulpwood trees. Its wood is soft, light, weak and close-grained, but it decays quickly. P. candicans (Balm-of-Gilead) is a hybrid or variety of the Balsam Poplars. The buds and leaves of these trees have a fragrant, balsamic odor. The Balm-of-Gilead has heart-shaped leaves with rounded, slightly hairy leaf stalks. The leaves are from 3 to 5 inches across and the perimeters are shallowly and finely serrated. The top is smooth and dark green and the other side has fuzzy veins and is paler. This tree grows up to 60 feet high with a diameter of 1 to 3 feet. It forms a broad, open crown. P. alba (White Poplar) is a handsome tree that grows from 80 to 90 feet. The leaves are dark green above and covered with thick, silvery-white fuzz underneath. The young shoots are also covered with felt. The leaves grow from 2 to 4 inches in length and their edges are irregularly and coarsely toothed or lobed resembling a maple leaf. The wood of many Poplars has significant commercial value. It is widely used as a source of pulpwood and for the manufacture of matchsticks, matchboxes, fruit and flower baskets, and much more. P. deltoides, the Eastern Cottonwood, is a native from Quebec to Florida and Texas. The leaves of this Cottonwood are broadly triangular-ovate or deltoid and sometimes slightly heart-shaped. They are from 3 to 5 inches long and glossy dark green on top and pale and smooth underneath with thin, translucent, toothed edges. This tree grows from 50 to 100 feet high. It is the largest of the Poplars. More varieties will be mentioned below.

Pot Cultivation

Poplars should be set in their permanent positions by the time they are 3 or 4 years old. They may be planted in the fall, winter or spring. They need moist, loamy soil and won't thrive on ground containing too much iron. If the ground tends to become waterlogged, plant your trees on mounds 1� to 2 feet high. Many kinds endure quite a bit of exposure and thrive near the sea. While the tree is young, all unwanted branches should gradually be removed from the lower portion of the trunk. A reasonably long length of trunk free of branches is the goal; the single trunk being carried well into the head of the tree. The head should have an even shape and be made of strong branches. Pruning should be done in the summer or fall because winter and spring pruning causes Poplars to bleed. All wounds should be protected with tree-wound paint.

Propagation

Seeds are small and usually sparingly produced. They lose their vitality quickly, so they should be planted as soon as they are ripe. It is more common to increase these trees by using cuttings of well-ripened, one-year-old wood, 9 to 12 inches in length. This should be done in the fall and they should be inserted in moist soil outside. It is smart to keep the trees to single shoots.

P. tomentosa	P. Tacamahaca

VARIETIES

• P. tremula (European Aspen);
• P. tremuloides (Quaking or Trembling Aspen);
• P.tremuloides pendula (Parasol de St. Julien);
• P. grandidentata (Large-toothed Aspen of North America);
• P. alba (White Poplar or Abele);
• P. tomentosa;
• P. canescens (Gray Poplar);
• P. nigra (Black Poplar);
• P. nigra italica (Lombardy Poplar);
• P. nigra betulifolia (Birch-leaved Poplar);
• P. canadensis (Carolina Poplar);
• P. canadensis aurea (Golden-leaved Poplar);
• P. Tacamahaca (Balsam Poplar or Tacamahac);
• P. trichocarpa (Western Balsam Poplar);
• P. deltoides (Cottonwood);
• P. Sargentii (Great Plains Cottonwood);
• P. Wilsonii;
• P. lasiocarpa;
• P. szechuanica;
• P. koreana.